Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations already declare readOnly, idempotent, non-destructive, closed-world behavior, so safety is covered. The description then adds real value by disclosing the content of the result (expected points, form, price, ownership), which matters because no output schema exists.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

A single sentence that front-loads the trigger condition before the payload list. No filler, no redundancy with the title or schema.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

For a two-parameter read-only tool with no output schema, the description supplies the key missing piece — what the comparison returns — and the usage trigger. Minor gap: it doesn't note behavior at the 3-player cap or how ties/missing players are handled.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is 100%, so both 'names' (2-3 players) and 'horizon' (1-8 gameweeks) are already documented. The description's 'coming gameweeks' wording loosely corresponds to horizon but adds no syntax or format detail beyond the schema, so the baseline of 3 applies.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

Names a specific verb+resource ('Compare FPL players') and enumerates exactly what is compared: expected points over coming gameweeks, form, price and ownership. This distinguishes it from siblings like get_player and find_players, which retrieve single players rather than a side-by-side comparison.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

Gives a concrete trigger scenario and a natural-language example ('Saka or Palmer?'), which is exactly the agent's decision context. It does not, however, name an alternative (e.g. use get_player for a single player) or state exclusions, so it falls short of the 5 bar.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.